The estimated 84 million US adults with prediabetes can significantly reduce their risk of developing type 2 diabetes mellitus (T2DM) by engaging in a Diabetes Prevention Program (DPP) or using metformin. Although these evidence-based interventions are widely available, few patients who would benefit use them. An opportune time to increase engagement of patients with prediabetes in strategies to prevent T2DM is after they are detected through a screening. One scalable and sustainable way to increase patient engagement after screenings would be to offer patients financial incentives for participating in a DPP or using metformin. Such financial incentives could be made more effective by integrating insights from behavioral economics with principles of self-determination theory (SDT). This integration could be achieved by adding to incentives automated tailored messages that link incentives and T2DM prevention to people's roles, values, and strengths. Our team of experts in T2DM prevention, behavioral economics, and SDT will conduct a 12-month pragmatic randomized controlled trial in which we will randomize 380 patients with prediabetes to 1 of 4 groups: (1) financial incentives plus tailored messages based on SDT principles; (2) financial incentives alone; (3) tailored messages based on SDT principles alone; or (4) an enhanced control group. Aim 1: Compare the effectiveness of financial incentives plus tailored messages based on SDT principles, financial incentives, and tailored messages based on SDT principles in decreasing hemoglobin A1c, weight, and waist circumference and in increasing participation in a DPP or use of metformin. We will assess changes in the primary outcome of hemoglobin A1c and in secondary outcomes of weight and waist circumference at 6 and 12 months. We will use health insurance claims data to measure the secondary outcome of participation in a DPP or use of metformin. Aim 2: Identify mediators and moderators of the effectiveness of financial incentives plus tailored messages based on SDT principles, financial incentives, and tailored messages based on SDT principles. To measure these, we will survey participants at baseline, 6, and 12 months. Aim 3: Evaluate facilitators of and barriers to scalability, acceptability, and sustainability of financial incentives plus tailored messages based on SDT principles, financial incentives, and tailored messages based on SDT principles. We will interview patients, workplace health promotion staff, and health system staff to conduct a comprehensive evaluation of program implementation and sustainability using an integration of the Reach, Effectiveness, Adoption, Implementation, and Maintenance and Consolidated Framework for Implementation Research frameworks. If effective, this novel approach that leverages insights from behavioral economics and SDT could serve as a model for how health care systems and community organizations can partner to help at-risk patients prevent T2DM as well as modify other behavioral risk factors for chronic disease and poor health.